THE PIGEON. 



255 



diameter, and at the junction of the two there is a strong 

 ventral flexure : it is marked ventrally with a median longi- 

 tudinal groove, separating the ventral pyramids : on the 

 upper side are the dorsal pyramids, which, passing from 

 behind forwards, diverge, leaving a median dorsal hollow, 

 the fourth ventricle (Fig. 59, v.4). 



TV ff . o7f 



Fig. 58. — Columba livia. The train. A, from above ; B, from 

 beneath ; C, from the left side ( x 2). 



cb, cerebellum : c.k, cerebral hemispheres : f, flocculus : inf, infun- 

 dibulum : m.o, medulla oblongata : o.l, optic lobes : olf, olfactory lobes : 

 o.i, optic tracts : fn, pineal body : II-XII, roots of cerebral nerves : 

 sji.l, root of first spinal nerve. 



